Yeah, if one admin wants to make a 100% secret poll with other admins.
Per usergroup is the best option. So admins wouldn't know (or would? this could be an option too) other admin votes, but would know mods. Mods the same.. And both of course would see users votes.
Or even, just know who voted on that poll, but not on witch option.

"As long as they are going to steal it, we want them to steal ours."Bill Gates speech at the University of Washington, as reported in "Gates, Buffett a bit bearish" CNET News (2 July 1998)